Monthly Archives: March 2011

This is one of the smaller objectives plus only the PVLAN concepts and practices are new – VLAN support remains relatively unchanged from VI3 (although the vDS and it’s associated VLAN support is new).

Knowledge

Identify types of VLANs and PVLANs

Skills and Abilities

Determine use cases for and configure VLAN Trunking

Determine use cases for and configure PVLANs

Use command line tools to troubleshoot and identify VLAN configurations

Types of VLAN

VLANs are a network standard (802.1q) which are fully supported in vSphere. They can be used to minimise broadcast traffic and as a security measure to segregate traffic (although like any technology there are weaknesses). Typical uses for VLANs with vSphere are to isolate infrastructure (vMotion, iSCSI and NFS) traffic and VM traffic.

In the Cisco world you set a port to be an ‘access port’ or a ‘trunk port’ if it’s going to carry multiple VLANs. VLAN IDs are 16 bit values giving a range of 0-4095. 4095 is used within vSphere to mean ‘all VLANs’ and is how you configure a portgroup when using VGT.

Configuring VLANs and VLAN trunking

For standard vSwitches you configure VLAN tags on portgroups. This configuration is done at the ESX host using the VI client (Configuration -> Networking);

The VCAP-DCA lab is still v4.0 (rather than v4.1) which means features such as NIOC and load based teaming (LBT) aren’t covered. Even though the Nexus 1000V isn’t on the Network objectives blueprint (just the vDS) it’s worth knowing what extra features it offers as some goals might require you to know when to use the Nexus1000V or just the vDS.

Network basics (VCP revision)

Standard switches support the following features (see section 2.3 for more details);

NIC teaming

Based on source VM ID (default)

Based on IP Hash (used with Etherchannel)

Based on source MAC hash

Explicit failover order

VLANs (EST, VST, VGT)

vDS Revision

The vDistributed switch separates the control plane and the data place to enable centralised administration as well as extra functionality compared to standard vSwitches. A good summary can be found at GeekSilver’s blog. Benefits;

NIC teaming is configured at the dvPortGroup level but can be overridden at the dvPort level (by default this is disabled but it can be allowed). This applies to both dvUplink Portgroups and standard dvPortGroups although on an uplink you CANNOT override the NIC teaming or Security policies.

I’m covering the troubleshooting objectives last while preparing for the VCAP-DCA – it seems like the logical thing to do. Learn all the material then play with it, break it, fix it, recreate it etc. Practice makes perfect! I’ve been using the Trainsignal’s Troubleshooting for vSphere course but the official VMware Troubleshooting course has been getting good feedback.

vpxd-xxxx.log.gz are archived logs. You have to unzip them to see contents.

You can change the logging level (which defaults to ‘normal’) by going to vCenter Server Settings -> Logging Options. This VMwareKB describes how to enable trivia logging in vCenter (even if vCenter isn’t running) although this may have a performance impact and should only be used temporarily while diagnosing issues.

Managing storage capacity is another potentially huge topic, even for a midsized company. The storage management functionality within vSphere is fairly comprehensive and a significant improvement over VI3.

Knowledge

Identify storage provisioning methods

Identify available storage monitoring tools, metrics and alarms

Skills and Abilities

Apply space utilization data to manage storage resources

Provision and manage storage resources according to Virtual Machine requirements

Storage is an area where you can never know too much. For many infrastructures storage is the most likely cause of performance issues and a source of complexity and misconfiguration – especially given that many VI admins come from a server background (not storage) due to VMware’s server consolidation roots.

Supported HBA types

This is a slightly odd exam topic – presumably we won’t be buying HBAs as part of the exam so what’s there to know? The best (only!) place to look for real world info is VMware’s HCL (which is now an online, searchable repository). Essentially it comes down to Fibre Channel or iSCSI HBAs.

Remember you can have a maximum of 8 HBAs or 16 HBA ports per ESX/ESXi server.You should not mix HBAs from different vendors in a single server. It can work but isn’t officially supported.

Disclaimer

These rants and raves are solely my opinion and do not reflect the opinions of my employers.
Any of my code, configuration references, or suggestions should be researched and verified in a lab environment before attempting in a production environment.
Agreement to use any of my code or recommendations removes me from any liability as such....and I shamelessly stole this disclaimer from Jase McCarty's site!